The high-profile case involved Sharon Coleman who claims she was forced to quit her job at London firm Attridge Law after she asked for time off to look after her disabled son.

Lawyers believe the decision will lead to a flood of claims from employees claiming discrimination from their employers because they also act as carers.

Mrs Coleman, who claimed managers at Attridge Law called her “lazy” when she requested time off to care for her son, accepted voluntary redundancy but later brought a claim for constructive dismissal and disability discrimination.

An employment tribunal referred the case to the European Court of Justice to clarify European law and it was ruled that anti-discrimination laws that protect disabled people in the workplace cover their carers as well.

Today, the EAT ruled that UK discrimination laws must take into account the legal protections under European law.

Public sector workers can rely on the Framework Directive to protect their rights but private sector workers could not do so.

They had to rely on the UK’s own domestic discrimination law - the Disability Discrimination Act (DDA) - which did not seem to accommodate the ECJ’s interpretation of the Framework Directive.

In November 2008, an employment tribunal decided that words could be read into the DDA so as to provide the same protection as the Framework Directive, but that decision was not binding on other tribunals.

Attridge Law appealed against the decision on the grounds that the tribunal had “distorted and rewritten” the DDA.

Today, Mr Justice Underhill, president of the Employment Appeal Tribunal, dismissed the appeal.

He said existing laws could be made to comply with the ECJ ruling by “reading in” words to the legislation - a process to achieve the “purpose and effect of a directive”.

These words include: “A person... discriminates against a person if he treats him less favourably than he treats or would treat another person by reason of the disability of another person.”

Catherine Casserley, a disability discrimination barrister from Cloisters, said: “This finally ends the long-running dispute about whether all workers - both in the private sector and the public sector - are protected from direct discrimination or harassment because of an association they may have with a disabled person.

“This decision is binding and will have to be taken into account in future legal cases. Hundreds of thousands of carers amongst others will benefit.

“This decision is also groundbreaking because the judge read into the Disability Discrimination Act whole new subsections in order to provide the necessary protection. As far as I know, it is the first time such a large amount of new text has been added to a domestic statute in order to comply with EC law.”

Mrs Coleman’s claim for damages for unfair dismissal will continue at an employment tribunal now that the law has been clarified.